Microwave-synthesized carbon dots from mangosteen peel for enhanced photoacoustic imaging using a low-cost near-infrared diode laser

Abstract

Carbon dots (CDots) from mangosteen peel exhibit distinct photoluminescent properties. Researchers utilize CDots as fluorescence biosensors. This study focuses on enhancing the absorbance of CDots in the near-infrared (NIR) region. The synthesis of CDots uses a microwave-assisted method without additional chemical treatments. The approach varies irradiation power and time to increase optical absorption. Successful synthesis of CDots is confirmed by UV–Vis and fluorescence spectroscopy, showing characteristic absorption and excitation-dependent emission. HRTEM analysis reveals spherical morphology with an average diameter of 2.070 ± 0.738 nm, while FTIR spectra indicate surface functional groups such as hydroxyl and carbonyl. A visible color change in solution and blue-to-green luminescence under 395 nm UV Light further confirm the formation and optical activity of the CDots. The extinction coefficient reaches 10.66 Lmol⁻1 cm⁻1. The thermal conversion efficiency measures 89.34%. Photoacoustic imaging tests reveal increased acoustic signal intensity under higher laser power and prolonged exposure. The maximum increase reaches 4.0%. The introduction of CDots enhances acoustic signal generation in samples. Signal intensity increases by 8.9% in agar and 15.3% in chicken tissue. These results confirm the effectiveness of CDots in producing photoacoustic signals. Researchers propose the use of mangosteen-derived CDots for NIR-based medical imaging. Future applications include non-invasive diagnostics and molecular-targeted imaging.